What is AES encryption?
AES (Advanced Encryption Standard) is the symmetric cipher used worldwide for protecting sensitive data — the same standard used by governments and banks. This tool uses AES-GCM, an authenticated mode: as well as hiding the contents it proves they have not been altered.
Which AES key size should I use?
AES-256 is the default and the right answer for almost everything. AES-128 is marginally faster and still far beyond any practical attack. There is no AES-192 option, because Chromium's Web Crypto refuses 192-bit AES keys — offering it would be offering something that does not work.
What happens if I use the wrong key?
You are told. AES-GCM verifies every block, so a wrong key fails at the first one and the tool says so instead of handing you a corrupt file. If the first block verifies and a later one fails, the key is proven correct and the file itself has been altered — and the message says that instead. Nothing is ever written to disk on a failure.
How should I manage my encryption keys?
Keep the key somewhere other than the encrypted files themselves. The Save key file button writes a small text file next to your ciphertext name, which you can store in a password manager, on a separate drive, or on paper. Copying the key into a password manager works just as well.
Is my data secure during encryption?
Everything happens in your browser through the Web Crypto API. Your files, your key and your password never leave the device, there is no upload step, and the tool works with the network disconnected.
Can I encrypt files as well as text?
Yes. Drop any file type, or paste text into the box under the drop zone. Text results come back as base64 you can copy straight into a message, and files come back as a download.
How large a file can I encrypt?
Files are read and written in 1 MiB blocks rather than loaded whole, so there is no fixed memory ceiling. The practical limit is how much your browser is willing to store for the finished file, which varies by device and by how much is already stored — if it is reached you are told, and nothing is saved.
What happens if I lose my encryption key?
The data is gone. There is no recovery path, no reset and no back door — that is what makes the encryption worth anything. Save the key before you close the tab.
